Tissue ablation is a medical procedure commonly used to treat conditions such as cardiac arrhythmia, which includes atrial fibrillation. For treating cardiac arrhythmia, ablation can be performed to modify tissue, such as to stop aberrant electrical propagation and/or disrupt aberrant electrical conduction through cardiac tissue. Although thermal ablation techniques are frequency used, such as cryoablation and radiofrequency (RF) ablation, non-thermal techniques such as pulsed field ablation (PFA) may also be used.
Pulsed field ablation involves the application of short pulsed electric fields (PEF), which may reversibly or irreversibly destabilize cell membranes through electropermeablization but generally do not affect the structural integrity of the tissue components, including the acellular cardiac extracellular matrix. The nature of PFA allows for very brief periods of therapeutic energy delivery, on the order of tens of milliseconds in duration. Further, PFA may not cause collateral damage to non-target tissue as frequently or as severely as thermal ablation techniques. Additionally, pharmacologic agents may be preferentially introduced into the cells of targeted tissue that are exposed to PEF having reversible membrane permeablization.
However, all intracardiac stimulation, recording, and ablation catheters are affected by cardiac motion, respiratory motion, device stiffness/maneuverability, and random patient movements. These sources of motion affect the quality of electrode contact with, for example, the heart wall. During energy delivery to ablate the target tissue, this motion can reduce effectiveness of such deliveries during the periods when the electrodes move away from the target tissue.
It is therefore desirable to provide a system and method for evaluating the quality of electrode-tissue contact. More specifically for PFA, it is desirable to provide a system and method for delivering energy to target tissue only when the electrodes are in good proximity to the target tissue and the timing within the cardiac cycle is optimal. This differs from the requirement for good thermal contact with tissue when using RF energy to perform hyperthermal ablations. Effective ablation of tissue using PFA only requires that the electric field must encompass the targeted area of ablation in order to cause ablation. In a similar manner, reversible permeablization effects may be imposed in target tissues when PEF encompasses the targeted area of tissue.